Apparatus for detecting the condition of an opaque band-shaped material travelling on a delivery system

ABSTRACT

An apparatus for detecting the parallelism between the lengthwise edge of an opaque band-shaped material travelling on a delivery system relative to the longitudinal axis of the delivery system wherein a first and a second detector are spatially arranged along the lengthwise edge, in the direction of travel of the lengthwise edge on the delivery system, so as to detect the position of the lengthwise edge, each detector including light projector and a light receiver facing said projector across the lengthwise edge of the travelling material. Each light receiver preferably includes an aggregate of numerous fine optical fibers and numerous photoelectric conversion elements connected to the individual fibers. Outputs from the first and second detectors are conducted from the numerous photoelectric conversion elements supplied with light from the light projectors to two input terminals of a differential amplifier which in turn generates outputs for detecting the parallelism of the edge of the bandshaped material travelling on the delivery system.

United States Patent 1191 Emura et al.

1 51 Feb. 11, 1975 APPARATUS FOR DETECTING THE CONDITION OF AN OPAQUEBAND-SHAPED MATERIAL TRAVELLING ON A DELIVERY SYSTEM [75] Inventors:Tokumatsu Emura, Yokohama;

Shigeo Kawabata, Tokyo; Takashi Shimoma, Yokohama, all of Japan [62]Division of Ser. No. 348,111, April 5, 1973, Pat. No.

[52] US. Cl 250/561, 250/548, 250/571 [Sl] Int. Cl G0ln 21/30, G06k11/02 [58] Field of Search 250/548, 561, 571, 560

[56] References Cited UNITED STATES PATENTS 2,643,l17 6/1953 Frisbie etal. 250/548 FOREIGN PATENTS OR APPLICATIONS 144,035 4/1961 U.S.S.R250/560 lllt Primary Examiner-Eli Lieberman Assistant ExaminerT. N.Grigsby Attorney, Agent, or FirmFlynn & Frishauf [57] ABSTRACT Anapparatus for detecting the parallelism between the lengthwise edge ofan opaque band-shaped material travelling on a delivery system relativeto the longitudinal axis of the delivery system wherein a first and asecond detector are spatially arranged along the lengthwise edge, in thedirection of travel of the lengthwise edge on the delivery system, so asto detect the position of the lengthwise edge, each detector includinglight projector and a light receiver facing said projector across thelengthwise edge of the travelling material. Each light receiverpreferably includes an aggregate of numerous fine optical fibers andnumerous photoelectric conversion elements connected to the individualfibers. Outputs from the first and second detectors are conducted fromthe numerous photoelectric conversion elements supplied with light fromthe light projectors to two input terminals of a differential amplifierwhich in turn generates outputs for detecting the parallelism of theedge of the bandshaped material travelling on the delivery system.

1 Claim, 22 Drawing Figures LIGHT FROM LIGHT PROJECTOR 7 3.866.053'SHEET 10F 6 FIG 1 SHEARING MACHINE PATENTEI] FEB] 1 [975 FIG. 3

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IIIIII II IIIIIIIIIIIII IIIII u IIIIIIIIIIIIII llllllIlllIlll APPARATUSFOR DETECTING THE CONDITION OF AN OPAQUE BAND-SHAPED MATERIAL TRAVELLINGON A DELIVERY SYSTEM CROSS-REFERENCE TO RELATED APPLICATION This is adivision of Ser. No. 348,111 filed Apr. 5, 1973, now U.S. Pat. No.3,833,816, issued Sept. 3, 1974.

BACKGROUND OF THE INVENTION This invention relates to an apparatus fordetecting the parallelism of the edge of a continuous opaque band-shapedmaterial such as a rolled steel strip or a sheet of paper travelling ona delivery system relative to the longitudinal axis of the deliverysystem.

Where a steel strip rolled by a roll assembly is conducted to a shearingmachine through a delivery system so as to be cut into the prescribedsize, it is desired that the cutter blade of the shearing machine bepreviously positioned perpendicular to the central axis of the deliverysystem. If, in this case, the central axis ofa travelling rolled steelstrip and that of the delivery system are parallel with each other, thenthe cut sides of the steel strip will be at right angles to thelengthwise edge thereof. Conversely, where the central axis of thetravelling steel strip and that of the delivery system are renderednonparallel with each other, it will be impossible to obtain a steelstrip of exact rectangularity. Hitherto, where determination is to bemade of the rectangularity of cut pieces ofa rolled steel strip, somesamples of said pieces are taken at random off the delivery system andsaid determination has been carried out for each sample, using, forexample, a dial gauge. This procedure not only consumes a great deal oftime and presents difficulties in total measurement, but also results inthe decreased operating efficiency due to the sampling of cut pieces ofrolled steel while shearing is continued. Further, said procedure failsto attain accurate determination, so that where a rigid tolerance isdemanded for the rectangularity of cut pieces of rolled steel, theprocedure is found substantially incapable of meeting such demand.

This invention has been accomplished in view of the above-mentionedcircumstances and is intended to provide an apparatus for detecting thecondition of an opaque band-shaped material travelling on a deliverysystem which measures the parallelism between the central axis orlengthwise edge of an elongate opaque band-shaped material such as arolled steel strip or a sheet of paper travelling on a delivery systemand the central axis of said system so as to detect the travellingcondition of said material, thereby determining on line therectangularity of the cut sides of, for example,-the rolled steel stripto its lengthwise edges.

SUMMARY OF THE INVENTION According to an aspect ofthis invention, thereis provided an apparatus for detecting the parallelism between thelengthwise edge of an opaque band-shaped material travelling on adelivery system relative to the longitudinal axis of the deliverysystem, comprising a first and a second detector spatially arrangedalong the lengthwise edge in the direction of travel of the lengthwiseedge on the delivery system so as to detect the position of saidlengthwise edge, each detector including a light projector and a lightreceiver facing said projector across the lengthwise edge of thetravelling material; and means for generating a signal indicating theparallelism of the lengthwise edge of the band-shaped materialtravelling on the delivery system upon receipt of outputs from saidfirst and second detectors.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic diagram showingthe arrangement of the delivery system of this invention for conductinga rolled steel strip; 4

FIG. 2 is a perspective view of a first and a second detector accordingto an embodiment of the invention spatially arranged along one of thelengthwise edges of the travelling rolled steel strip;

FIG. 3 illustrates the relative position of the edge of a rolled steelstrip to the first and second detectors when the central axis of saidstrip is displaced from that of the delivery system;

FIG. 4 is a perspective view of a light receiver included in thedetectors of FIGS. 2 and 3, showing the detailed construction of saidreceiver;

FIG. 5 shows an optical fiber of FIG. 4 where light is projected on thelight receiving surface of said fiber;

FIG. 6 is a curve diagram showing the property of a photoelectricconversion element to convert light to electric signals;

FIG. 7 indicates the concrete arrangement of a photoelectric conversioncircuit included in the detectors according to the embodiment of FIG. 2;

FIG. 8 shows the concrete arrangement of a switching circuit used incombination with the photoelectric conversion circuit of FIG. 7;

FIG. 9 is a block circuit diagram of a detecting apparatus according tothe embodiment of FIG. 2;

FIG. 10 illustrates the principle on which a detector according toanother embodiment of the invention is based;

FIG. 11 is a block circuit diagram of a detecting apparatus using thedetector of FIG. 10;

FIGS. l2Al2C and 13A-I3C show the wave forms of output signals from thefirst and second detectors of FIG. 11, respectively; and

FIGS. I4A-14E indicate the wave forms of signals by way of illustratingthe operation of the embodiment of FIG. 11.

DETAILED DESCRIPTION OF THE INVENTION There will now be described thepreferred embodiments of this invention where there is used theapparatus of the invention for detecting the condition of a rolled steelstrip travelling on a delivery system, thereby determining-therectangularity of the cut sides of the strip to its lengthwise edges, asobtained during the shearing operation. It will be noted, however, thatI the invention is not limited to this application, but may also be usedin detecting the condition of a sheet of paper travelling on a deliverysystem installed in, for example, a paper mill, thereby attaining theaccurate rectangularity of the cut sides of the sheet of paper to itslengthwise edges.

Referring to FIG. 1, a rolled steel strip 1 is made to travel in thedirection of the indicated arrow by a pinch roll assembly 3 through alevel roll assembly 2 to a shearing machine 6 after passing a first anda second detector 4 and 5. Though, according to FIG. 1, the level rollassembly 2 and pinch roll assembly 3 collectively form a delivery systemfor a steel strip 1, it is possible to construct said delivery system byadditionally providing a side guide roll assembly (not shown) to controlthe crosswise shifting of the travelling steel strip.

As seen from FIG. 2, the first detector 4 comprises a light projector 7and a light receiver 9 facing said projector 7 across one of thelengthwise edges 8 of a rolled steel strip 1. Part of the light from thelight projector 7 is shut off or blocked by said lengthwise edge 8 ofthe steel strip 1, the remainder directly reaching the light receiver 9.The second detector is placed on the lengthwise edge 8 near the entranceto a shearing machine 6, at a point spaced a prescribed distance of, forexample, 550 mm from said first detector 4. Like the fi'rst detector 4,the second detector 5 comprises a light projector 10 and a lightreceiver 11. Both first and second detectors 4 and 5 are arranged, asshown in FIG. 3, at a prescribed interval D in parallel with the centralaxis OO of the delivery system, Where, therefore, the lengthwise edge 8or the central axis 8-8 of the rolled steel strip 1 is parallel with thecentral axis OO of the delivery system, then the cut sides of said steelstrip 1 will be kept at right angles to its lengthwise edge 8. However,if the lengthwise edge 8 or central axis 8-8 of the steel strip 1 isinclined, as shown in FIG. 3, from the central axis OO of the deliverysystem, then the above-mentioned rectangularity will be inaccurate. Nowlet it be assumed that the distance from the outer end of the lightreceiver 9 of the first detector 4 to that edge 8 of the steel strip 1which faces said light receiver 9 is X1 and that the distance from theouter end of the light receiver 11 of the second detector 5 to that edge8 of the steel strip 1 which faces said light receiver 11 is X2. Thenthe difference between both distances will be XI X2 d. If, therefore,the interval D between both detectors 4 and 5 is previously fixed, thenthe magnitude of said difference d will immediately indicate the degreein which the central axis S5 or lengthwise edge 8 of the steel strip 1is displaced from the central axis O-O of the delivery system. The firstembodiment of this invention electrically determines the difference (Ion line. The light receiver 9 of the first detector 4 contains, asillustrated in FIG. 4, a bundle 14 of numerous optical fibers 13. Eachof the optical fibers 13 is a fine element shaped into a thin elongateelement with the longer side of the cross section measured to be, forexample, 5 mm and the shorter side of the cross section to be 0.05 to0.10 mm. These thin elements 13 are laminated into the aforesaid fiberbundle 14. The top side of the fiber bundle 14 constitutes the lightreceiving surface of the light receiver 9, and the bottom side isoptically connected to a plurality of photoelectric conversion elementsprovided so as to face the respective optical fibers 13. Now let it beassumed that the region of the fine fiber element 13 other than thehatching of FIG. 5 is supplied with light and the shorter side of thelight receiving surface 15 of said element 13 has a length of e and theshorter side of that region of said light receiving surface 15 which isactually exposed to light has a length of 5. Then from the ratio 8/6 awhich the length of the shorter side of the region actually exposed tolight bears to the length of the shorter side of the entire lightreceiving surface 15, and from the condition that the intensity of lightprojected from the light projector 7 is constant, outputs from thephoto-electric conversion element have been experimentally found to havesuch a relationship as expressed by the curve of FIG. 6 with respect tothe valve A of said ratio.

To attain accurate determination in the first embodiment, it isnecessary to quantize the output from the photoelectric conversionelement which corresponds to the area of that region of the lightreceiving surface 15 of said element 13 which is actually exposed tolight. To this end, it is advised to designate an output of, forexample, more than 50% as l and an output of, for example, less than 50%as O and, in this case, to provide the output side of the photoelectricconversion element with such a switching element as is renderedconducting when an output from said photoelectric conversion elementamounts to more than 50%.

FIGS. 7 and 8 jointly illustrate a photoelectric conversion circuitcontaining the above-mentioned switching element. This circuit comprisesa plurality of photoelectric conversion elements or phototransistors16-1 to l6-n optically connected to the corresponding optical fiberelements 13. The collectors of said phototransistors 16-1 to l6-n arecollectively connected to the output terminal (for example, +6 volts) ofa constant voltage source 17. Photoelectric conversion outputs from theemitters of said phototransistors 16-1 to 16-n are conducted to thecorresponding amplifiers 18-1 to l8-n for amplification. Outputs thusamplified cause the corresponding indication lamps 19-1 to l9-n to giveforth light, and at the same time actuate the corresponding relays 20-1to 20-n.

These relays 20-1 to 20-n are so designed as to commence operation whenoutputs from the photoelectric conversion elements 16-! to 16-n accountfor more than 50% of the curve of FIG. 6. Since the photoelectricconversion elements 16-! to 16-n present somewhat varying properties,the amplifiers 18-1 to I8-n are so designed as to have the degree ofamplification adjusted so as to enable the relays 20-1 to 20-n to beoperated at such points as well match the varying properties of thephotoelectric conversion elements 16-] to 16-n,

The contacts 20-1a to 20-na of the relays 20-1 to 20-n are connected, asshown in FIG. 8, in series to variable resistors 21-] to 21-n. Twocircuits consisting of serially connected contacts 20-la to 20-na andserially connected variable resistors 21-] to 21-n respectively areconnected in parallel with each other. Said parallel connected circuitsare supplied with outputs from a voltage setting circuit 22 operatedwith output voltage from the constant voltage source 17 of FIG. 7.Outputs from said parallel connected circuits are conducted through anamplifier 23 to the output terminal 24 of the switching circuit of FIG.8. Said output terminal produces such a magnitude of voltage ascorresponds to the total amount of light supplied to the optical fibers13 of the light receiver 9. Another detector 5 similarly consists of thelight receiver 11, photoelectric conversion circuit and switching unit.

Received light beams from the light receiver 9 of the first detector 4are converted, as shown in FIG. 9, to

electric signals by a first photoelectric converter 25 including thephotoelectric conversion elements 16-! to 16-11 of FIG. 7, and thensupplied to one input terminal ofa comparison circuit 27 through a firstswitching unit 26 including relays 20-1 to 20-n shown in FIG. 7.Similarly, received light beams from the light receiver 11 of the seconddetector 5 are converted to electric signals by a second photoelectricconverter 28 including the photoelectric conversion elements 16-! to16-n of FIG. 7, and then conducted to the other input terminal of thecomparison circuit 27. This comparison circuit 27 consists of, forexample, a differential amplifier and is so designed as to produce anoutput corresponding to a difference between the voltages of theabovementioned two inputs of comparison circuit 27. Namely, an outputfrom said comparison circuit 27 represents a difference d between thelengths X1 and X2 of those parts of the first and second light receivers9 and 11 which are supplied with light (as defined in connection withFIG. 3). An output from the comparison circuit 27 is transmitted to anaverage circuit 30. Since a steel strip 1 passes the first and seconddetectors 4 and 5 at a relatively high speed, outputs from saiddetectors 4 and 5 vary one moment after another due to the fineroughness of the edge portion of the rolled steel strip 1. Sampling ofsuch momentarily changing outputs is not of practical advantage due tothe difficulty of effecting accurate determination. According to thisembodiment, therefore, the values of outputs from the detectors 4 and 5are averaged per prescribed length of time by the average circuit 30.This average circuit 30 is, for example, a timer circuit which consistsof an integration capacitor actuated for a prescribed length of time Tto integrate outputs from the comparison circuit 27 and a divisioncircuit for dividing outputs from said integration capacitor by saidprescribed length of time T. The division circuit produces an average ofthe values of outputs from the comparison circuit 27 An output from theaverage circuit 30 is normally supplied to a display unit 31 and, ifnecessary, to an alarm unit 32. Thus, indication is made in an amountcorresponding to the magnitude of the difference d of FIG. 3, and wheresaid difference d exceeds a prescribed value,,an alarm is given by saidalarm unit 32.

If, during the shearing of a steel strip 1 travelling on a deliverysystem, an operator adjusts the position of the strip 1 so as to makethe central axis SS of the strip 1 parallel with that OO of the deliverysystem, namely, to reduce the aforesaid difference to zero, whilelooking at readings on the display unit 31, then there will be obtaineda steel strip 1 whose cut sides are made perpendicular to the lengthwiseedge.

In the foregoing embodiment, the light receiver includes optical fibers,so that the minute determining capacity of the detector of thisinvention depends on the side of the entire light receiving surface ofeach of said optical fibers. If said light receiving surface has an areaof, for example, 5 mm X 0.05 to 0.10 mm as shown in FIG. 4, then theextent of displacement of a travelling steel strip determinable by saiddetector will be 50 to I00 microns. Though it may be desired to elevatethe minute determining capacity ofthe detector of said embodiment usingoptical fibers by minimizing their size, yet it is extremely difficultto reduce the shorter side of the optical fiber to, for example, l0microns, failing to put said detector to practical application in highprecision determination.

FIG. illustrates a detector 40 according to another embodiment of thisinvention which is improved in the above-mentioned respect. FIG. 10 onlyshows said detector 4a, because the other detector 5a is of the samearrangement. There will now be described the arrangement and operationof said detector 4a. Parallel light L transmitted from the lightprojector 7 of FIG. 2 is focused by an object lens 33 and enters theopening 35 ofa view mask 34. On the inside ofa scanning drum 37 facingthe opening 35 of the view mask 34 is disposed a focusing lens 36. Abeam of light focused by the focusing lens 36 is projected on the lightreceiving surface of a photoelectric conversion element 38. The scanningdrum 37 has a plurality of, for example, four scanning slits 39, whichenable scanning to be effected on the opening 35 of the view mask 37from the top to the bottom with the rotation of the scanning drum 37 inthe direction of the indicated arrow. Near a point on the outerperiphery of the scanning drum 37 are provided a lamp 40 and focusinglens 41 so as to face a photoelectric conversion element 42 across thewall of said drum 37. All the above-mentioned members 40 to 42constitute a synchronizing signal generator.

When one lengthwise edge 8 of the steel strip 1 is positioned at R in ascanning range of El-EZ, an image of R is focused at r within theopening 35 of the view mask 34. When one of the slits 39 of the scanningdrum 37 passes r as the result of its rotation in the direction of theindicated arrow, then parallel light L from the light projector 7 isreceived by the photoelectric conversion element 38, an output pulsefrom which rises at El and falls at E2 as illustrated in FIG. 12A. Whenthe scanning drum 37 further rotates, the scanning slit 39 passes thephotoelectric conversion element 42, producing a synchronizing pulse ina timing shown in FIG. 12B.

Referring now to FIG. 11, light from the first light projector 7 isconducted, as in FIG. 10, to a first detector 4a and outputs from thephotoelectric conversion elements 38 and 42 of FIG. 10 are transmittedto a first wave shaping circuit 45, where said outputs jointly form anoutput, as shown in FIG. 12C, obtained by having the rear edge of thepulse of FIG. 12A extended up to the point of the synchronizing pulse ofFIG. 123. This is intended to prevent the unstable timing of the rearedge of the output pulse of FIG. 12A due to the irregular position ofthe scanning slits 39. Namely, the synchronizing pulse of FIG. 12Battains the proper timing of said rear edge. If necessary, the waveshaping circuit 45 may be provided with a preamplifier. Light from thesecond light projector 10 is supplied to a second detector 5a of thesame arrangement as the first one 4a. An output from the second detector5a is sent to a second wave shaping circuit 46. Now let it be assumedthat an output pulse from the second detector 5a presents, as shown inFIG. 13A, asmaller width than that of FIG. 12A. Then an output havingthe wave form shaped by the synchronizing pulse of FIG. 13B becomes suchan output as is narrower than the pulse of FIG. 12C and has the rearedge synchronized with that of the pulse of FIG. 12C.

Outputs from the first and second wave shaping circuits 45 and 46 aretransmitted to a first and second AND gate respectively together withclock pulses from a clock pulse generator 47. Now let it be assumed thatan output from the first wave shaping circuit 45 takes the form of FIG.14A, an output from the second wave groups of minor pulses having awidth corresponding to an output pulse from the first detector 4a andthat from the second detector 50 respectively.

Clock pulses of FIGS. 14D and 14E are supplied to a subtracting gate 50which produces an output representing a difference between the numbersof clock pulses of FIGS. 14D and 14E. The number of output pulses fromsaid subtracting gate 50 expresses the magnitude of the difference d ofFIG. 3. The embodiment of FIG. 11 is further provided with a third ANDgate 51 so as to generate upon receipt of an output pulse from saidsubtracting gate 50 a signal instructing the withdrawal from thedelivery system of those cut pieces of a steel strip taken out of theshearing machine 6 of FIG. 1 which are found to have the improperrectangularity of the cut sides. A certain length of time is generallytaken for those parts of a steel strip 1 whose travelling conditionshave been detected, for example, by the first and second detectors 4 and5 of FIG. 1 to be delivered from the shearing machine 6 after being cutthereby. If some portions of the steel strip 1 are previously determinedby the detectors 4 and 5 that they have travelled on the delivery systemwith the central axis or the lengthwise edge displaced from the centralaxis of the delivery system, probably resulting in the improperrectangularity of the cut sides, then rejection of such disqualified cutpieces should be effected exactly at the moment they have passed throughthe shearing machine 6. Otherwise, well-qualified cut pieces of a steelstrip would perchance be rejected together with offgrade pieces. Toavoid such erroneous rejection, therefore, the embodiment of FIG. 11 isprovided with a counter 52 for counting pulses generated by a pulsegenerator with the rotation of the shearing machine 6. When the cutterblade of the shearing machine 6 is brought exactly to a cutting positionafter making one rotation, said counter 52 supplies a carry signal tothe AND gate 51. Namely, when some portions of a steel strip 1 whichhave been detected to be disqualified are conducted toian entrance tothe shearing machine 6 ready to be cut thereby, the AND gate 51 isopened to produce an output, which is supplied to another AND gate 54together with an output from an upper-lower limit level setter 53. Thislevel setter 53 is intended to detect whether a number of minor pulsesrepresenting the difference betweenthe numbers of output minor pulsesfrom the first and second detectors 4a and 5a falls within a prescribedlimit. If the difference exceeds the limit, said AND gate 54 supplies analarm signal to an upper-lower limit alarm unit 55. An output from theAND gate 51 is conducted to a display unit 56 to indicate the travellingcondition of the steel strip 1 andfurther to a rejection output unit 57for its actuation, thereby unfailingly effecting the proper rejection ofdisqualified cut pieces of the steel strip 1 from the delivery system.

Exact coincidence between the portions of a steel strip 1 whosetravelling conditions have previously been detected by the detectors andthe cut pieces of said strip just after leaving the shearing machine,whether rejected or approved, can be confirmed by other means than theaforesaid process of actuating a pulse generator with the rotation ofthe cutter of the shearing machine 6, for example, from a signaldenoting the running speed of the delivery system and the prescribedlength to which the steel strip 1 is to be cut up by the shearingmachine. If, in the latter case, the running speed of the deliverysystem changes, the above-mentioned coincidence can be established allthe same.

As mentioned above, the minute determining capacity of the embodiment ofFIG. 10 depends on the fre quency of clock pulses and the number ofrotations of the scanning drum, so that said embodiment can effect a farmore minute determination of the displacement of the central axis or thelengthwise edge of a travelling steel strip from the central axis of thedelivery system, for example, to an extent of 10 microns than when thelight receiver consists of optical fibers. Where the scanning drum 37rotated at the rate of 2,000 rpm, and was perforated with four slits 39each having a width of 50 microns and clock pulses had a frequency of200 KHZ, then the detector of this invention attained as minutedetermination as :5 microns.

What we claim is:

1. An apparatus for detecting the parallelism between the lengthwiseedge of an opaque band-shaped material travelling on a delivery systemand the longitudinal axis of said delivery system which is set at aright angle to the cutting blade of a shearing machine to which theband-shaped material is to be delivered,

, comprising a first and a second detector spatially arranged along saidlengthwise edge, in the direction of which it travels on the deliverysystem so as to detect the position of said edge, each detectorcomprising a first lens for focusing light from a light projector, aview mask bored with an opening in that section where light is focusedby said first lens, a second lens for further focusing the light imagealready obtained in the view mask, a photoelectric conversion elementdisposed in a position where light is focused by the second lens, ascanning drum located between the view mask and the second lens andperforated with at least one scanning slit and a synchronizing pulsegenerator associated with said scanning drum; and the means forgenerating a signal indicating the parallelism of the band-shapedmaterial comprises means for shaping the wave form of outputs from thefirst and second detectors, a clock pulse generator, a first and asecond AND gate supplied with outputs from the wave shaping means andclock pulse generator, a subtracting gate designed to produce a signalrepresenting the difference between the numbers of output pulses fromthe first and second AND gates, a counter for counting a number ofpulses generated with the rotation of the cutter of the shearingmachine, an AND gate supplied with carry signals from the counter andoutputs from the subtracting gate, and a display unit, an upper-lowerlimit alarm unit and a rejection output unit, the three last-mentionedmembers being supplied with outputs from the last-mentioned AND gate.

UNITED STATES PATENT OFFICE QETIHCATE 0F QQREQTWN PATENT NO. 1 3 053DATED I February 11, i INVENTOWS) i Tokumatsu EMURA et al it iscertified that error appears in the ab0ve-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Add priority data as follows:

[30] Foreign Application Priority Data April 6, 1972 Japan ..3467i/72--.

igned an fialfidldis fifth of August1975 [SEAL] Arrest:

1. An apparatus for detecting the parallelism between the lengthwiseedge of an opaque band-shaped material travelling on a delivery systemand the longitudinal axis of said delivery system which is set at aright angle to the cutting blade of a shearing machine to which theband-shaped material is to be delivered, comprising a first and a seconddetector spatially arranged along said lengthwise edge, in the directionof which it travels on the delivery system so as to detect the positionof said edge, each detector comprising a first lens for focusing lightfrom a light projector, a view mask bored with an opening in thatsection where light is Focused by said first lens, a second lens forfurther focusing the light image already obtained in the view mask, aphotoelectric conversion element disposed in a position where light isfocused by the second lens, a scanning drum located between the viewmask and the second lens and perforated with at least one scanning slitand a synchronizing pulse generator associated with said scanning drum;and the means for generating a signal indicating the parallelism of theband-shaped material comprises means for shaping the wave form ofoutputs from the first and second detectors, a clock pulse generator, afirst and a second AND gate supplied with outputs from the wave shapingmeans and clock pulse generator, a subtracting gate designed to producea signal representing the difference between the numbers of outputpulses from the first and second AND gates, a counter for counting anumber of pulses generated with the rotation of the cutter of theshearing machine, an AND gate supplied with carry signals from thecounter and outputs from the subtracting gate, and a display unit, anupper-lower limit alarm unit and a rejection output unit, the threelast-mentioned members being supplied with outputs from thelast-mentioned AND gate.